1. Technical Field
The present invention relates generally to a production method of a stator coil for use in an electric motor to be mounted in, for example, automotive vehicles, and an electric motor equipped with a stator coil produced by the production method.
2. Background Art
Japanese Patent First Publication No. 2009-194994 (corresponding to US2009/0199393 A1, assigned to the same assignee as that of this application) discloses a stator coil production method which bends an insulator-coated conductor wire several times to form a stator coil conductor which is equipped with in-slot portions to be disposed within slots of a stator core and coil-end portions each of which extends between every adjacent two of the in-slot portions and will be a portion of a coil end when the stator coil conductor is wound through the slots of the stator core. This method is achieved using at least three die-punch pairs which are arrayed at regular intervals along a travel path on which the insulator-coated conductor wire travels. The die and the punch of each pair are opposed to each other across the travel path. Specifically, the die and the punch of one of the die-punch pairs are brought close to each other to clamp and press a portion (as will also be referred to as a preplanned coil end portion below) of the insulator-coated conductor wire to form the coil end portion. Simultaneously, the other die-punch pairs are moved in a direction perpendicular to the travel path to form the in-slot portions leading from the coil-end portion.
The above stator coil production method includes two steps: one is to input the insulator-coated conductor wire between the die and the punch of each die-punch pair prior to the step of forming the coil end portion and the other is to remove or output the insulator-coated conductor wire from the die-punch pairs after the step of forming the in-slot portions. Such inputting and outputting steps consume much time to move the dies and the punches because of the insulator-coated conductor wire is long, thus resulting in an increase in time required to complete the stator coil conductor. Additionally, the handling of the insulator-coated conductor wire is complicated, which leads to decreased productivity thereof.